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Electrostatics is the study of charges. There are two different types of charges. One is a positive charge, and the second is a negative charge. In electrostatics, we get to know about electric charges, electric fields, electrostatic forces, etc.
Electrostatics is the part of physics which gives us detailed information about the static charge.
The electric field is the force exerted by the unit charge. The relationship between force (F) and electric force (E) is given by,
The electric field unit is Newton/Coulomb (N/C).
Electric charge is a physical property of matter for which a force is experienced due to an electromagnetic field.
Electrons are negatively charged, and protons are positively charged. Both are the unit of the matter.
Electric flux is a hypothetical concept. According to the concept, the positive charge emits electric flux, and the negative charge receives electric flux.
Gauss’s theorem
Gauss’s theorem is one of the most important theorems to calculate electric flux.
The total flux through a closed surface is equal to the 1/ε times of the amount of charge enclosed by the surface.
The mathematical form of Gauss’s law is
Where,
Φ= electric flux
Q = total charge enclosed by the surface
ε= permittivity of the medium
The unit of permittivity is
The attractive and repulsive force between particles due to electric charges is known as the electrostatic force.
Coulomb’s law
The force of attraction between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between the charges.
Where,
This is also known as Coulomb’s constant. The S.I unit of Coulomb’s constant is
F = Force
q = charge
r = distance between the charges
Charge density
There are three types of charge density:
Linear charge density: The charge distribution along the length is known as linear charge density.
Surface charge density: The charge distribution along the surface is known as surface charge density.
Volume charge density: The charge distribution along the volume is known as volume charge density.
Electrostatics problems and solutions
Question 1: Two equal magnitude charges have 19 N force in between them. They have been kept 8 cm apart. Find the magnitude of the charges.
Solution:
The given data is,
Force, F = 19 N
Distance, r = 8 cm = 0.08 m
Let the magnitude of the charges be q
By applying Coulomb’s law,
q = 3.67x 10-6C
The magnitude of both the charges is 3.67 x 10-6 C each.
Question 2: Find the magnitude of the electric field when the charge is 
Solution:
The given data is,
The magnitude of the charge,
The magnitude of the force field, F = 6.2 N
By using the relationship between Force (F) and electric field (E), we get
So, the magnitude of the electric field is 
Solution:
If the charges have the same magnitude and the type of the charges is similar, then the null point will be at the centre. The electric flux of the two charges will be opposite in direction.
Problem 4: There is a hollow sphere and a solid sphere of the same radius. Which one contains more charge?
Solution:
The hollow sphere and the solid sphere have an equal radius. So, the surface area of the hollow sphere and the solid sphere is equal. The charge stays on the surface. Therefore, both the hollow sphere and the solid sphere have an equal amount of charges.
Problem 5: Which vertex has maximum surface charge density in a charged cube?
Solution:
A cube has six surfaces and eight vertices. The Cube is a uniform figure. So, all its eight vertices have an equal amount of charges. No particular vertex has maximum surface charge density in a charged cube.
Problem 6: Where the charge density is maximum- on the surface or at the corner of an object?
Solution:
At the corner of an object, the charge density is maximum. On the surface, the charge is distributed on a surface. In the sharp or pointed edges, the density of the charges is maximum.
Conclusion
Electrostatic problems are based on the electric flux, electric charges, electric force field, electric field, electric potential, etc. Electric flux is a hypothetical concept, and the electric force is the force of attraction between different charges and the force of repulsion between the same charged particles. Electric potential is nothing but the potential difference between two charges. The potential difference between the two points helps the flow of electric charge. Due to potential differences, the electric charge flows from high potential to low potential.
